We have identified dual adhesion systems in the surfaces of chick embryonic retina and optic tectum cells, and have prepared antibodies and adhesion-inhibiting Fabs directed against each. The two systems are mutually non-recognizing and could in principle function as coordinate systems for Cartesian mapping of retina onto optic tectum. We are now determining whether these systems are distributed in gradients on the retinal and tectal surfaces. We are also attempting to prepare monoclonal antibodies against each adhesion system. With these, we hope to resolve the cell surface localization of each of the two adhesion systems at the ultrastructural level. We are continuing our study of the guidance of amphibian pronephric duct migration by a wave of changing adhesiveness that, according to our evidence, passes posteriad across the embryonic flank at precisely the speed at which new somites become segmented. We are seeking a role for fibronectin in normal morphogenetic processes. Finally, we are applying our newly developed Cahn balance/parallel plate compression procedure to the physical measurement of sigma's (cohesive energies) of embryonic cell aggregates of several kinds.